Nowadays, illumination devices that detect a light amount (light intensity) of a light source with a sensor and control lighting of the light source based on a detection result of the sensor are being developed.
A configuration in which a plurality of LED (Light Emitting Diode) chips, a light detection element serving as a sensor, a plurality of switching elements, and a controller are included, for example, has been known as a configuration that can be used in this type of illumination device (refer to Document 1 (JP 2009-206186A), for example).
The light detection element in Document 1 detects light that is emitted from the plurality of LED chips having different emission colors. The switching elements are respectively inserted in power supply paths to the corresponding LED chips. The controller separately adjusts light outputs of the plurality of LED chips by performing PWM control on the switching elements based on an output of the light detection element. The controller generates PWM signals such that mixed color periods in which all of the LED chips are lit and monitoring periods in which only one LED chip that is a monitoring target of the light detection element is lit alternately appear in time series.
In the configuration in Document 1, light from each of the LED chips of respective emission colors is accurately detected by successively switching LED chips that are lit as the monitoring target, and light outputs of the LED chips are adjusted.
Incidentally, a configuration of the illumination device in which variation in light output is further reduced is required, the variation is not sufficiently reduced by using the configuration in Document 1 described above, and as a result, further improvement is required.